This invention relates to systems, including methods and apparatus for the facilitation of the topical treatment of vegetation, or terrain therefor. Specifically, the invention is directed to small scale equipment and processes usable under local conditions to reliably apply plant agents by hand, as in the case of a hand held portable foam generator/applicator supplied with a source of low pressure water. Typically, the self-contained unit is coupled by means of an ordinary garden hose to a residential water supply.
Spray application of chemical agents is a familiar technology ranging from use for fire fighting to agricultural application from low flying planes, truck platforms or similar rigs. In such operations, a highly pressurized source of fluid is invariably supplied as from a hydrant or a pump, or by virtue of an ancillary airstream. System geometry of a complex nature, or internal vanes and the like are commonly required to generate the particular type of foam required.
Typically (see e.g. U.S. Pat. No. 2,492,037 to Freeman, et al or U.S. Pat. No. 3,424,250 to Thomae) foams of the fire fighting variety are of high expansion i.e. exhibit a high ratio of air to water and the spray configuration is that of a hollow cone ranging to a fog. Solid streams are usually desired for projection over a greater distance, although a solid stream does not ordinarily provide enough surface area to generate more than the wet, or low expansion type foam. See Timpson U.S. Pat. No. 2,146,605 and Lacks, et al U.S. Pat. No. 2,894,694.
Agricultural usage of this technology has been in many respects similar for large scale application where pressurized systems can be readily made available, and substantial utilization justifies the expense of considerable engineering. Control of rate of application is essential with most plant agents and additional ecological concern applies in the case of such materials as pesticides; hence potential difficulty with drift is evident, especially in relatively high expansion systems. Small particulate form may be pin-pointed as the most obvious source of tendency toward drift, and this is also associated with high expansion foam. Hence, Sachnik in U.S. Pat. No. 3,694,512 emphasizes foams having an expansion ratio much lower than that typical for fire fighting, covering the range only up to 16:1. The resultant foam has the form of globules on the order of 1/32 to 1/8 inch in diameter. Spraying systems disclosed in this and related U.S. Pat. Nos. 3,604,509; 3,618,856; and 3,701,482 rely on a pressurized fluid source or available airstreams. Guth, in U.S. Pat. No. 3,764,293 shows similar agricultural spraying with liquid droplets of at least 200 to 800 microns, to minimize drifting.
The principle utility of foams heretofore for both fire fighting and agricultural purposes is to serve as a blanket, of sufficient thickness to control air access, prevent volatilization of soil additives, or to minimize frost damage. More recently, it has been appreciated that the presence of the foam aids in visibility to establish coverage. However, no change has occurred in the practice of generating a composition substantially foamed throughout, which is applied as a coherent layer of appreciable thickness without lateral interruption. Such layers of foam are often undesirable in preventing access of air and light to the underlying substrate. Thus, grass may be so damaged even where the foam is dissipated over a short term.
The increased popularity of home gardening, and the expense of commercial servicing has activated interest in homeowner application of plant agents. U.S. Pat. Nos. 3,713,404, 3,871,130 and 3,922,977 of Lavo, et al. to the common assignee describe systems and methodology adapted to this interest, the texts of which are incorporated herein by reference. Disclosed is a method for the application of plant agents utilizing a garden hose coupled to a residential water supply providing a stream of water at a static pressure of about 15 to about 70 psig wherein the stream of water is introduced to a foam generation zone, a foam concentrate comprising a foaming agent and a plant agent is educted into the stream by a venturi arrangement, the mixture is mechanically agitated, and the proportion of water and foam concentrate controlled to maintain a dilution of 15 to 90 parts by volume of water to each part of concentrate, and the thus formed foam providing solution is then directed against a foraminous barrier through which a current of air is simultaneously and unidirectionally forced, whereupon the solution is spumed for application into a deformable foam.
While the equipment contemplated by Lavo et al. operates to effect the satisfactory broadcasting of foams in residential environments, it is desired to improve upon these designs. A principal objective in any such system is to maximize simplicity in construction and use. Accordingly, pressurization of the fluid source by pumps or use of air blast generators and the like is impractical. It will be understood that many of the internal geometric aspects of prior equipment operate efficaciously only in conjunction with pressurized fluids. Since homeowner operation is of necessity restricted to the low and often variable pressures available from the residential water supply coupled to a simple and economic foam generation system usable as a portable hand held device, different design considerations apply.
Applicants have now devised equipment and developed technology meeting such criteria, embodied in the following description.